The research in this thesis was conducted within the Bio-Informatics section
of the Faculty of Electrical Engineering at the University of Twente, in colla-
boration with Research and Innovation Department at the Rehabilitation Centre
"Het Roessingh" in Enschede.

-----------------------------------

In reply to Mike Whittle's posting on internal and external moments last week:
some information is available in David A. Winter's 1979 book "Biomechanics of
Human Movement" (Wiley-Interscience, New York - Chicester - Brisbane - Toronto).

-----------------------------------

Other points of confusion: when is my varus your valgus ?

An interesting item is Technical Report ISO/TR 9586:1988 (E) "Implants for
Surgery -- Usage of the terms `valgus' and `varus' in orthopaedic surgery" from
the International Organization for Standardization. It is a Type 3 report,
which is issued when "a technical committee has collected data from a different
kind from that which is normally published as an international Standard (`state
of the art', for example)". The reasons for publishing the document are provi-
ded in its Introduction:

This Type 3 Technical Report has been prepared in order to state the
differences in usage of the terms `valgus' and `varus' so that anomalies
of usage, especially in relation to the hip joint, may be clearly
understood and confusion minimized.

The Terminology Working Group (WG 1) of Technical Committee 150 (Implants
for Surgery) of the International Organization for Standardization (ISO)
has for some years been discussing the terms `valgus' and `varus' in an
attempt to reach agreed definitions. The terms have been in use for cen-
turies but their meaning seems to have varied from time to time. The
present usage has developed in a haphazard manner, such that consistent
definition of the terms seems to be impossible.

A discussion paper (document ISO/TC 150/WG 1 N 59) was prepared by ISO/TC
150/WG 1 and circulated widely throughout the world for comment. The results
of the study of the comments reveal that the terms are now so ingrained in
day-to-day use that it is most unlikely that they can be abandoned or
replaced by alternative terms.

Examples of different use of the terms are:

(1) distal deformities may be compensating for proximal deformities. Perhaps
the commonest example is where `hallux valgus' is associated with a `varus'
deformity of the first metatarsal.

(2) Varus and valgus osteotomy of the upper end of the femur. The confusion
appears to relate to whether the osteotomy is named after the deformity that
surgery is intended to produce, or after the deformity that the surgery is
intended to correct.

Some of the report's final recommendations are:

Since the terms `flexion' or `extension' deformities are common, there
is no real objection against the use of the terms `adduction' or `abduc-
tion' deformities. However, the concern about these two terms being so
similar (dictation or transcription errors) is of considerable importance
and would appear to be a definite drawback.

This Technical Report has been produced because of the significant
international differences in the use of the terms around the hip joint.
It does not appear that complete consensus will be reached in the fore-
seeable future, nor is it likely that the use of the terms will be dis-
continued, so it is important for all those working in the field of
orthopaedics te be aware of these differences.

It is strongly urged that authors should carefully define their usage
of `valgus' and `varus' whenever they use these terms in published work
concerning the hip joint and upper femur. Clinical teachers should draw
the attention of their students to the anomalies, and doctors should be
aware of the problem when transferring patients from country to country.
A simple drawing is probably the safest way of transmitting the information.

-----------------------------------

More points of confusion: when is my axis your axis ?

In the wake of the joint angle debate, I had the (mixed) pleasure of having to
retract a previous statement that the joint angle definitions between two clini-
cally relevant software packages for Gait Analysis are different, after a pres-
entation during the San Diego Conference mentioned by Mike Whittle last week.
As it turned out, there were different interpretations of the terms `sagittal,
coronal, and transverse axes'. It appeared that one interpretation was to
view these axes as normal to the planes of the same name, which would make the
sagittal axis identical to a (pure) flexion-extension axis, the coronal axis
identical to a (pure) ab-/ad-duction axis, and the transverse axis a (pure)
endo-/exo-rotation axis. However, Kapandji and many others view the sagittal
axis as a horizontal axis within the sagittal plane, the transverse axis as a
horizontal axis in the coronal plane, etc. Perhaps, ISO's TC 150 / WG 1 should
also address this terminological problem ?